True, but what you describe is related to the measurement and sampling accuracy. Until such sensors hit the Heisenberg uncertainty levels of precision on the re

True, but what you describe is related to the measurement and sampling accuracy. Until such sensors hit the Heisenberg uncertainty levels of precision on the readout/sensing, such uncertainties may be decreased further, there is no physical constrain on that (more sensors may help with that also). While it is in principle physically impossible to even identify the fact of movement linearly with constant speed without introducing external information (radar, GPS, wheels rotation, airspeed, magnetic and gravitational field change, Doppler shift in radio waves, etc). This is the relativity principle in action, which says that all the inertial frames of reference are equivalent.